Electrical precipitator



J n- 2 19 H. A. WINTERMUTE ELECTRICAL PRECIPITATOR 4 Sheets-Sheet 1Filed Oct. 15, 1952 ATTORNEY Jan. 25, 1955 H. A. WINTERMUTE 2,700,429

ELECTRICAL PRECIPITATOR Filed Oct. 15, 1952 I 4 Sheets-Sheet 2 INVENTORHARRY A. WINTERMUTE ATTORNEY Jan. 25, 1955 H. A. WINTERMUTE 2,700,429

ELECTRICAL. PRECIFITATOR Filed on. 15, 1952 4 Sheets-Sheet :5

INVENTOR HARRY A.WINTER MUTE ATTORNEY Jan. 1955 H. A. WINTERMUTE2,700,429

ELECTRICAL PRECIPITATOR Filed Oct. 15, 1952 4 Sheets-Sheet 4 INVENTORHARRY A.W|NTERMUTE ATTORNEY United States Patent ELECTRICAL PRECIPITATORHarry A. Wintermute, Plainfield, N. 1., assignor to ResearchCorporation, New York, N. Y,, a corporation of New York ApplicationOctober 15, 1952, Serial No. 314,802

8 Claims. (Cl. 183-7) This invention relates to the electricalprecipitation of suspended materials such as dust, smoke particles andcarboniferous particles, from bodies of gas in which they are suspended.It has been found that many types of present precipitators have a muchlower eificiency when treating coarse and carboniferous particles thanwhen handling particles of finer fractions. The difficulty of retainingsuch coarse and carboniferous particles on a collecting electrode platedepends, to a considerable extent, upon the velocity of the gases whichare being treated. If the gas velocity is reasonably high, then it isquite difiicult to collect the particles. Particular diificulty isencountered when the coarse particles contain a large proportion ofcoked material, which is often found to be the case in many commoninstallations. Some of the reasons these particles are difiicult tocollect are:

1. They do not agglomerate readily with other particles.

2. Their relatively large areas give them considerable sail effect.

3. The coked or carboniferous particles charge and discharge readily.Therefore, they bounce up and down along the surface of the collectingelectrode, and this property together with their sail effect causes themto dance along the surface and out of a precipitator unless collected bytrapping them in a pocket or receiving hopper.

It is a principal object of the present invention to provide a methodand apparatus for overcoming the above ditficulty. This is accomplishedaccording to the invention by causing the gases bearing the particles topass through a system of precipitating electrodes so arranged that notonly will the gases be caused to follow a tortuous path in theprecipitating field, but also their velocity will be greatly reduced inthis area. The tortuous path is so arranged that the gases tend to bemoved in a direction which will favor collection of the particles whilethe gases move in a different direction. Furthermore, thecross-sectional area of the path of motion of the gases in theprecipitating field is effectively larger in the vicinity of thecollecting electrode than it is in the vicinity of the dischargeelectrodes, thereby rendering the collecting electrode effective toprecipitate even the larger particles of the type above referred to.Also, the collecting electrodes are so arranged in a vertical plane thatparticles reaching them either fall into a hopper below the electrodesby gravity or are caught by traps which are arranged in the direction ofmotion of the particles, but not of the major portion of the gas. Thusthe particle is caught in one of these two ways, and cannot easilyescape.

The specific nature of the invention, as well as other objects andadvantages thereof, will clearly appear from a description of apreferred embodiment as shown in the accompanying drawings in which:

Fig. l is a sectional plan view taken on line 11 of Fig. 3 of one formof precipitator according to the invention;

Pig. 2 is a side elevation, partly in section, of the precipitator andits housing;

Fig. 3 is a sectional front view taken on line 3-3 of Fig. 2;

Fig. 4 represents an expanded perspective view of the discharge andcollector electrodes, respectively, of the modification of the inventiondisclosed in Fig. 1;

Fig. 5 is a perspective view of a different form of= "ice dischargeelectrode from that shown in Fig. 1, and adapted to be substitutedtherefor;

Fig. 6 is a schematic sectional view of the electrodes including thedischarge electrode shown in Fig. 5, with a mechanical rectifier shownat the supply source;

Fig. 7 is a view similar to Fig. 6, except that the discharge electrodeis of the form shown in Fig. 1, and an electronic discharge type ofrectifier is shown instead of a mechanical rectifier.

Referring to Fig. l, the precipitator is shown housed in a shell orcasing 1, which may be inserted in a duct 31 through which the gases tobe treated are passing. Discharge electrodes 2 and collector electrodes3 are suitably supported within the housing by means Which will bedescribed in detail below. Collector electrodes 3 are in the form ofextended surface members formed of screen material, perforated sheetmaterial or expanded metal so as to provide a large number ofperforations through which the gas and suspended material may readilypass. in a plurality of V-shaped configurations as clearly shown in'Fig.1 and Fig. 5, and have no sharp points on the surface so that they willnot give a corona discharge toward the opposite discharge electrodemembers 2. The discharge members 2 may be formed as a series oflouver-shaped members struck out of a single sheet of metal as bestshown in Fig. 4, or, alternatively, may be constructed of a number ofmetal angle members to be held together by plate or angle members 26.Although only two of these members 26 are shown for each angle member,one at the top and one at the bottom, it will be apparent that one ormore intermediate members may be provided for additional strength ifdesired. The edges of the discharge electrodes may be serrated as shownat 2e to provide corona discharge points where desired. Since thedischarge electrode members extend parallel to the collectingelectrodes, it will be apparent that they will, in general, convergetoward each other in the downstream direction. At the convergent end ofeach electrode structure is placed a precipitate or grit trap forcollecting precipitated particles, particularly the larger particleswhich may have been unable to adhere to the collecting electrodes 3, forthe reasons described above, and which are therefore carried generallydownstream along the collecting electrodes until they are accumulated bytraps 4. A pipe 5, best shown in Figs. 1 and 2, is provided forcollecting the precipitate and gas in which the particles are suspendedfrom trap 4. This is intended for installations with which an auxiliarycollector is used and may be dispensed with under most circumstances.However, in some installations, the use of such a collecting pipe andauxiliary collector may be found necessary. Individual legs 6 are runfrom the collector pipe 5 to the traps 4. The pipes are so dimensionedand arranged that uniform gas pressure is provided in each trap 4 toinsure even gas distribution for transporting the collected material, oralternatively, a damper may be supplied to each of the legs 6.

Supporting members 7 are provided at the gas inlet end for stiifeningthe collector electrodes, and additional stiffening bar supports 8 maybe used for maintaining uniform spacing between the opposing electrodes.At the bottom of the precipitator housing a dust receiver hopper isprovided. The electrode construction, as can be seen from the drawings,is open at the bottom and most of the finer precipitate will fall bygravity from the electrodes into this hopper. The usual vibration means,not shown, will be employed to facilitate this action. A screw or dragconveyor may be provided at the bottom of the hopper for removing thecollected material. If desired, a gas vacuum system can be used instead.

Baflle member 11a is connected to an electrical contact with thegrounded electrode members 2. Since this baffle extends upwardly in someplaces above the bottoms of the grounded electrodes 3 the bafile membersare cut away, as shown at 11c, to provide electrical clearance distancefrom the high potential electrodes 3. Baffle member 11b is connected toand in contact with the high potential electrode 3. The groundedelectrode 2 is there- The collector electrodes are arranged fore cutaway as shown at 2a in Figs. 2 and 4 to provide electrical clearancebetween this baffle, which is at high tension, and the groundedelectrode 2. Bafiie 12a is provided for closing off the area above theprecipitating zone and a similar baffle 12b is provided downstream atthe precipitator outlet for preventing gas sneakage above the electrodesafter the gases enter the precipitating zone. A third baffle 120 may beprovided midway between the gas inlet and outlet for preventing gassneakage above the precipitating zone. This baflie extends from the roofplate down to the grounded electrode member. In order to do this, acut-out 12d, sufiicient to give electrical clear ance, is supplied atthe top of the high potential electrodes. A horizontal baffle 13 isprovided at the bottom of the precipitator inlet for preventing gasesfrom entering the hopper Zone, and a corresponding bafiie 14 is locateddownstream to prevent gas sneakage through the hopper.

At the top of the precipitator housing are provided additional bushousings 15 for protecting the insulator and other high tension members,one such housing being shown for each set of transversely disposedinsulators 16. These insulators both insulate and support the weight ofthe high-tension electrodes 3 by means of vertical support members 18which are both electrically and mechanically fastened to electrode 3 bymeans of angle members 19 as shown, and are electrically connected atthe top of insulator to high voltage lead 22 which passes throughinsulating bushing 21, and is connected to the usual high voltagesource. An orifice ring 20 is provided through which the vertical bars18 pass, thus insuring adequate clearance to the grounded casing of theprecipitator housing. The ground connection to the housing is indicatedat 24, and a suitable high voltage lead is connected to the ground sideof the electrodes at 23, this lead running to the other side of the highvoltage source to which lead 22 is connected.

No electrode cleaning means have been shown. It will be. understood bythose skilled in the art that means such as vibrators can be attached toeach of the banks of discharge electrodes at the lower bars 26 in themodification of Figs. and 6 or the lower portion of the dischargeelectrode 2 in the modification of Fig. 2. A cross bar can also beattached to the tops of the high tension electrodes, which in turn isattached to a vibrator through an insulating means. All this is wellunderstood in the art and therefore in the interest of clarity isomitted from the drawing.

As best shown in Fig. 6, the dust-laden gas passing downstream alongduct 31, after passing through high tension electrode 3, is caused tocurve sharply back upon itself and thus follow a tortuous path asindicated by the arrows. The sharp backard turn is, of course,accomplished much more easily by the light gas molecules than by therelatively heavy suspended particles, especially those of larger size,which tend to be flung out in the direction shown by the smaller arrows28. At the same time, these particles, when passing in the vicinity ofthe grounded discharge electrodes 2 acquire a charge in the usualfashion which also tends to cause them to move in the electrostaticfield back toward the perforated high tension electrode 3. Thecombination of both of these forces is effective where the electrostaticfield alone would not be in the case of larger particles to attract mostof them toward high tension electrode 3. Even such particles as are notdefinitely attractedso as to cling to the collector electrode 3 will bemoved by the downstream component of the gas current in the vicinity ofelectrode 3 toward its downstream apex. At this point, if the particlesbecome separated from the collector electrode, it will be apparent thatthey are now in a low gas velocity region, and can readily be caught bytrap 4 in which the particles now find themselves. If collector tube 5is employed, the low-velocity gas containing a high concentration oflarge size particles will move down pipe 6 to pipe 5 for completeprecipitation in another stage, the gas now being at a sufficiently lowvelocity to make this easily possible. For many types of installationthis will not be found necessary and the precipitate can be successfullytrapped at 4 to fall into the bottom of the dust-receiving hopper 9 fromwhich it may be suitably conveyed by a screw or drag conveyor- It willbe noted in Fig. 6 that the cross section available for gas flow at thebase or outlet side. of grounded electrode 21 issmaller than near the.discharge. points. Thus it will. be.- seen that in this modification,the velocity of the gas is necessarily greater near the broadened baseof the grounded discharge electrode 2 than near the point thereof, dueto the inherent shape of the orifices provided by the series ofdischarge electrodes. This effect still further tends to decrease thevelocity of the gas in the critical region near the discharge points,and thus make the electrical field still more effective in acting uponthe larger particles. In the modification shown in Figs. 1 and 7 thiseffect is not as great, since the apertures provided at 2c by thecut-out portions of the sheet from which the louvers 2d are struckprovide almost as great a cross section available for gas flow as isfound in the region near the discharge points of the electrodes.However, this effect is somewhat compensated for by the fact that theangle of reversal is even sharper in this modification than in that ofFig. 6, and this sharp reversal of the gas flow tends to be veryeffective in exerting centrifugal force on the particles to. preventthem from freely following the course of the gas flow, and tends to movethem down toward the apex 3a of the high tension electrode 3. Figs. 6and 7 also show respectively, by way of example only, the use of amechanical rectifier 34 or an electronic discharge device 35 for whichpurpose Kenetron rectifiers have been successfully employed.

It will be noted that the shape and arrangement of the precipitatorelectrodes themselves are utilized to change the path of current gasflow in such a manner as to enhance the effect produced by theelectrical discharge between these electrodes. This had been found to bevery effective in removing a range of particles including larger sizeswhich have heretofore required an additional mechanical removal step.

It will be apparent that the embodiments shown are only exemplary andthat various modifications can be made in construction and arrangementwithin the scope of the invention as defined in the appended claims.

I claim:

1. Electrical precipitator apparatus comprising a gas passage,aperturedcollector electrode means disposed across said gas passage soas to require dust-laden gas from. said passage to pass through theapertures of said electrode means, discharge electrode means downstreamfrom and opposite to said collector electrode means, said dischargeelectrode means comprising a plurality of louver- ]ike dischargeelectrodes having a series of sharp loci disposedin a surface parallelto said collector electrodes to define a discharge field between saidopposed electrodes, said discharge electrode means being substantiallyparallel to each other and set at such an angle relative to saidcollector electrode surface as to define a series of re-entrant gaspassages between adjacent ones of said discharge electrodes for sharplychanging the direction of flow of gas from the apertures of thecollector electrode while said gas is in the discharge field between theelectrodes.

2. The invention according to claim 1 including mechanical. particletrap means located adjacent said precipitator electrodes ina directionopposite said direction of flow through said louver-like dischargeelectrodes, whereby dust particles which cannot follow the sharp changein direction of the gas in said discharge field are caught by saidtrapmeans.

3. The invention according to claim 2, said trap means being downstreamof said collector electrodes, said collector electrodes being verticallydisposed, and additional hopper means disposed below said collectorelectrodes for receiving particles by gravity from said collector means.

4. The invention defined in claim 2, said apertured electrode meanscomprising two substantially planar perforated electrode membersarranged in the form of a 1 with the apex pointing downstream, said trapmeans being located near the apex of said V'.

5. The invention according to claim 3 including flue means in. said trapmeans for collecting a concentrated mixture of gas at low velocity anddust particles from said trap. means.

6. The invention according to claim 1, each of said louver-likedischarge electrodesv being wedge-shaped with the base downstream andthe sharpened edge constituting the discharge: electrode; lecus.

7, The? invention. defined in; claim 6, said sharpened 5 6 edge beingserrated to constitute a series of discharge Refgrences Cited in thefile of this patent points.

8. The invention defined in claim 1, each of said UNITED STATES PATENTSlouver-like discharge elements being slat-shaped and c0m- 2,357,734Hafer Sept. 5, 1941 prising adjacent slats struck out of a single sheetof con- 5 FOREIGN PATENTS ducting material.

545,605 Germany Mar. 3, 1932

